1. Field of the Invention
This invention relates to high-precision distance measuring systems and techniques. More specifically, the invention is a high-precision, laser Fresnel distance measuring system and method.
2. Description of the Related Art
Non-intrusive and highly accurate determination of distance to a “target” with a precision on the order of a micron or less would be useful in a variety of industrial, commercial, and government-related applications. For example, large adaptive mirrors used in space or ground applications require knowledge of the location of mirror segments to a very high precision in order to make corrections to an optical wavefront.
Conventional high-precision rangefinders can use lasers and complex processing systems/algorithms. For instance, U.S. Pat. No. 6,456,383 discloses a method and apparatus for making absolute distance measurements using Fresnel diffraction. Briefly, after a laser beam is reflected by a target, the reflected beam is passed through an aperture. A detector spaced from the aperture detects the central intensity of the beam (passed through the aperture) as well as intensities displaced from the beam's center. The intensities are then used to calculate the distance to the target using complex mathematical relationships. However, this system is limited to determination of distances on the order of a few centimeters.